One of the biggest critics of Michael Dell’s plan to take the company he founded private has launched a fresh challenge to that $24.4 billion bid and says the slumping PC maker needs new leadership.

Billionaire investor Carl Icahn has teamed with Dell’s largest independent shareholder, Southeastern Asset Management, to pitch a deal that would let Dell shareholders keep their stake in the company and give them either $12 per share in cash or additional shares.

Icahn and Southeastern say this alternative, which would keep the company publicly traded, gives shareholders a stake in future company gains, according to a May 9 letter sent to Dell’s board.

An investment group led by Michael Dell offered earlier this year to pay $13.65 per share in a deal that would take the Round Rock, Texas, company private. But Icahn said Friday during a CNBC interview that price amounted to a giveaway.

“It’s really a travesty,” he said. “It’s almost like something out of Saturday Night Live.”

Icahn and Southeastern heaped more criticism on Dell’s offer in the letter. They accused the Dell board of insulting shareholder intelligence by claiming to be focused on shareholders’ best interests while accepting Dell’s offer to buy the company for “far below what we consider its value to be.”

“You not only sanctioned Michael Dell’s offer, which amazingly allows him to purchase the company from shareholders with their own money but, to add insult to injury, you have agreed to give Mr. Dell a breakup fee of up to $450 million,” the letter states.

A special committee of Dell Inc.’s board said in a separate statement that it is carefully reviewing the proposal from Icahn and Southeastern “to assess the potential risks and rewards to the public shareholders.”

Icahn and Southeastern say they would pay for their offer with existing cash from the company and about $5.2 billion in debt, which would be less than Michael Dell’s plan requires.

Company documents outlining Dell’s buyout proposal state that it would involve a $2 billion loan from Microsoft Corp. and up to $13.75 billion in other debt from lenders.

Southeastern and Icahn said they own about 13 percent of the company’s outstanding shares. They want the Dell board to put their proposal before shareholders instead of proceeding with Dell’s buyout offer. If the board declines, they want the vote on Michael Dell’s buyout combined with the company’s annual meeting to elect new directors. Then they’ll challenge Dell’s board with their own director nominees.

If Dell puts Michael Dell’s buyout proposal up for a shareholder vote, Icahn and Southeastern promise to work “assiduously” to convince the other shareholders to reject the bid, which he made with the investment firm Silver Lake.

“This company has suffered long enough from very wrong-headed decisions made by the board and its management,” the letter states. “Do not make another by putting the company through an unnecessary debilitating proxy fight.”

“Allow the shareholders to decide for themselves which offer they choose,” Icahn and Southeastern wrote.

Dell Inc. plans to hold a special meeting to vote on Michael Dell’s buyout proposal sometime in its current quarter, which ends Aug. 2. It then expects to close the deal in the next quarter. The company usually holds its annual meeting, where shareholders vote on directors, among other items, in the summer.

Icahn told CNBC he is confident they can convince shareholders to vote against Michael Dell’s proposal. He noted that they already have their 13 percent as a “no” vote, and Dell cannot vote his 16 percent stake in the company.

Icahn said that if his board candidates are elected, he guarantees Michael Dell will no longer run the company.

“It’s amazing what can be done once you do change the leadership,” he said.

PC sales have been declining as people delay replacing desktop and laptop computers and spend money instead on smartphones and tablet computers. Michael Dell believes he can turn around the company by diversifying into more profitable niches such as business software, data storage and consulting. The company founder wants to do this without worrying about Wall Street’s fixation on short-term results.

But Southeastern and Icahn said in their letter that all company shareholders should benefit from a turnaround, not just Michael Dell. They said the company can rein in costs and can expand beyond its core business. They also noted that the company has growth potential in emerging markets like China, India and Brazil.

“We truly believe the best days for Dell are yet to come and the company has a tremendous opportunity to build on its strong platform,” the letter states.

Icahn told CNBC that while the personal computer business is declining “Dell is not just a PC company.”

Major shareholders started expressing their unhappiness with Michael Dell’s offer shortly after the company announced it in early February. Dell has said in regulatory filings that 25 lawsuits have been filed challenging the proposed buyout, a few of which have already been voluntarily dismissed.

A competing bid from buyout specialist Blackstone Group LP then emerged. But Blackstone said last month that it had dropped its plan to buy most of Dell’s outstanding stock for $14.25 per share due in part to the slumping PC market.

Icahn has made three pitches to Dell so far. He said in March he wanted the company to pay a special dividend of $9 per share if shareholders reject the buyout offer. He then made a preliminary proposal to buy 58 percent of Dell stock for $15 per share.

Dell shares rose 11 cents to $13.43 in Friday afternoon trading. The stock has ranged from $8.69 to $15.81 over the past year.

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